Theoretical Evidence For a Ninth Planet Beyond Pluto May Be Premature (forbes.com)

An anonymous reader writes: Earlier today, the team of Pluto-killer Mike Brown and Konstantin Batygin announced that they had found evidence of a ninth planet in our Solar System beyond the orbit of Pluto, larger and more massive than even Earth. However, a closer inspection of the work shows that they predict a few things that haven't been observed, including a population of Kuiper belt objects with large inclinations and retrograde orbits, long-period Kuiper belt objects with opposite ecliptic latitudes and longitudes, and infrared data showing the emission from such an outer world. There are many good reasons to be skeptical, and not conclude that there's a ninth planet without more (and better) evidence.

Comments

Forbes doesn't like AdBlock

[Kazymyr]

Oh well. Article will go unread.

Re:Forbes doesn't like AdBlock

[Rei]

I don't use AdBlock and yet Forbes thinks I'm using it. So I can't read it.

But I can say, at least the infrared claim doesn't hold up. Wise ruled out Saturn-sized bodies out to 10k AU (based not on reflection but, due to the distances, more the internal heat they'd give off), but here we're talking about a body that's far smaller than Saturn and would have much less internal heat. The theoretical planet is 1/10th the mass of Saturn, and its IR from internal heat would be much less than that. And while one could argue that due to being closer its additional solar reflection would overcome that, I wouldn't be so sure. Neptune is 1,7x heavier than the theoretical planet yet still has a cross sectional area less than 18% that of Saturn. And you can't just scale down by that 1,7x to around 10% the cross sectional area of Saturn - it's probably much less because its colder (the reason why Neptune has a smaller radius than Uranus despite being heavier). And even more than what you'd get simply from cooling gases - at aphelion it could well be cold enough to chill liquid hydrogen out of its atmosphere into hydrogen seas. And that would make it dramatically smaller.

In short, if it's even remotely near aphelion, WISE could well have missed it. And elliptical-orbiting bodies spend much more of their time near aphelion than perihelion.

As for the required observations about KBOs, I don't know enough about the types of bodies and their orbits being referred to in the summary to know if we should already have seen them or not. But either way, we need *something* to explain the similar arguments of perihelion of the sednoids. It's hard enough just to explain how something with such a distant perihelion ended up in an elliptical orbit to begin with, let alone multiple such objects sharing similar arguments of perihelion.

Re:Forbes doesn't like AdBlock

[avandesande]

It says right in the article that Wise had a hard time detecting Neptune which is relatively close.